by Anton Shilov
01/08/2014 | 10:13 PM
At the Consumer Electronics Show event Advanced Micro Drives has publicized some of the details behind the code-named “Kaveri” accelerated processing unit (APU). The firm revealed that it had to make rather tough design decisions when developing the new hybrid chip and had to choose a manufacturing technology that had been optimized for highly-integrated chips.
For previous generations of its high-performance APUs (i.e., Llano, Trinity and Richland), AMD chose 32nm silicon-on-insulator process technology that was developed by the company itself and GlobalFoundries with high-performance microprocessor units in mind. Those process technologies allowed AMD to ensure high clock-speeds for its x86 cores, such as Bulldozer and Piledriver. Unfortunately, that manufacturing technology was not exactly tailored for high transistor density of graphics processing units. As a consequence, AMD had to make certain compromises, which did not allow it to integrate all the hardware it wanted.
With Kaveri, AMD chose to use GlobalFoundries’ 28SHP (28nm super high performance) process technology that was designed with various types of chips in mind. Improved transistor density and thinner elements of 28nm process tech allowed the company to integrate whopping 2.41 billion of transistors into a 245mm2 Kaveri die, which is 85% higher transistor count compared to Trinity/Richland design (246mm2, 1.303 billion transistors, 32nm SOI). Now the company has four Steamroller cores, hUMA [heterogeneous unified memory architecture] memory controller, Radeon graphics processing unit with 512 stream processors (AMD calls them eight GPU compute units) and a lot of various special-purpose hardware inside its flagship APU.
The high-density “universal” process technology has its drawbacks too: it lacks thick metal stacks that make possible to run microprocessors at high frequencies. As a result, the company sacrificed extreme clock-rates for x86 general-purpose processing cores in favour or forward-looking APU design with a strong focus on heterogeneous computing.
While overclockers and performance enthusiasts may not appreciate AMD’s choice, the company claims in its documents that thanks to more advanced Steamroller micro-architecture (with up to 20% higher instruction per clock [IPC] performance), the Kaveri will not be slower than currently-available Richland APUs and will even beat them in many cases.
AMD believes that thanks to scalability of its Kaveri design (which is supposed to be available in 15W – 95W thermal design power envelopes), it will be able to successfully address various personal computers, including desktops, notebooks and servers, with its new A-series accelerated processing units.